A powerful Mayan curse causes snakes to hatch in the stomach of a young woman, eating her inside out. She needs to get from Mexico to Los Angeles in order to have the curse lifted by a powerful Mayan shaman. On the brink of death she boards a train headed for L.A. Unfortunately the passengers are now trapped on board, and left to fall victim to these vicious, venomous vipers.
Some of Crystal and Williams' character dynamics were inspired by their HBO Comic Relief performances (with Whoopi Goldberg) of the late 1980s.